Post-column ethylation for the determination of ionic alkyllead compounds by high-performance liquid chromatography atomic absorption spectrometry

Abstract

A continuous post-column ethylate generator was used to interface a high-performance liquid chromatographic (HPLC) instrument with a quartz tube (QT) atomic absorption spectrometer for the determination of ionic alkyllead compounds (R3Pb+, R2Pb2+; R = CH3 or C2H5). Analytes were separated as their tetramethylenedithiocarbamate complexes, ethylated, purged from the crude reaction mixture and volatilised into the QT furnace with limits of detection which approached 0.1 ng. A half-replicate 25 factorial design (multivariate analysis) augmented with 11 data points to form a composite design was used to predict alkyllead ethylate response under the influence of five interacting reactor/detector variables. The system, which provided base-line separation of seven ionic alkyllead compounds, was approximately ten times more sensitive than a direct HPLC-thermospray-AAS interface. However the linear dynamic range of the response was limited to less than two orders of magnitude at optimum sensitivity. The system was also orders of magnitude less sensitive to Pb2+ than to ionic alkyllead compounds.